Effects of oxidative modification on thermal aggregation and gel properties of soy protein by malondialdehyde

Comparative study of the effects of ultrasonic power on the structure and functional properties of gliadin in wheat and green wheat

The impact of different ultrasonic power on the structure and functional properties of wheat gliadin (WG) and green wheat gliadin (GG) was investigated and compared. Ultrasound had no obvious effect on subunit composition and bands of WG and GG, and there were more small molecular weight bands in GG. The results of Fourier transform-infrared spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy analyses demonstrated that ultrasonic treatment had a significant effect on the structure of WG and GG, inducing the transformation from order structure to disorder structure. The dispersion and uniformity were better at 400 and 300 W, respectively. Under proper ultrasonic treatment, the particle size of WG and GG was significantly reduced, and the free sulfhydryl groups and surface hydrophobicity were significantly increased (p < 0.05). Furthermore, the functional properties of WG and GG such as solubility, emulsification properties, water holding and oil holding properties, thermal stability, and digestibility were enhanced. The better functional properties of WG and GG were obtained at 400 and 300 W, respectively. These results indicated that ultrasonic treatment with appropriate power was a valuable method for improving functional characteristics of WG and GG. PRACTICAL APPLICATION: Ultrasonic treatment could cause structural changes of wheat gliadin (WG) and green wheat gliadin (GG), and their functional properties are improved under appropriate power. This study compares the effects of ultrasound on WG and GG, and the results will provide theoretical guidance for the development of GG in the food industry.

High-power sonication of soy proteins: Hydroxyl radicals and their effects on protein structure

High-power sonication (HPS) is shown to alter protein structure, thus, its functionality, via intermolecular interactions. This study evaluated the effects of HPS on molecular structure of soy proteins in aqueous medium. Free radicals generated during HPS were quantitated using the 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) spin trap method. Electron paramagnetic resonance (EPR) was used to identify them as mostly hydroxyl radicals. The minimum saturation concentration of spin trap solution was determined to be 500 mM of DMPO in water, when exposed to 5 W/cm³ ultrasound power density (PD) for 10 min; subsequently, this concentration was used for quantitating radicals generated in protein samples. Five aqueous soy protein systems, namely, 5% soy protein isolate (SPI), 5% SPI without isoflavonoids (NO-ISO SPI), subunit solutions 1% glycinin (11S) and 1% β conglycinin (7S), and 10% soy flakes (w/v), were sonicated at 2.5 and 5 W/cm³ PDs. Only adducts of hydroxyl radicals (DMPO-OH) were detected in all of these aqueous systems. The highest concentration (3.68 µM) of DMPO-OH adduct was measured in 11S subunit solution at 5 W/cm³, whereas, the lowest (0.67 µM) was in soy flakes solution at 2.5 W/cm³. PD 5 W/cm³ generated higher concentration of radicals in 7S subunit solution, NO-ISO SPI, and soy flakes protein, compared to sonication at PD 2.5 W/cm³. No change in the protein electrophoretic patterns were observed due to HPS. However, some changes due to HPS were observed in the estimated secondary and tertiary structures, and the contents of free sulfhydryl groups and disulfide bonds in proteins.

A new style of fermented tofu by Lactobacillus casei combined with salt coagulant

This research provided a new way to improve the quality of tofu using lactic acid bacteria combined with salt coagulants. In this study, the effect of Lactobacillus casei (L. casei) combined with salt coagulants (MgCl₂, MgSO₄, CaCl₂, CaSO₄) on the yield, water-holding capacity (WHC), texture, sensory factors, microstructure and flavour were analysed to evaluate the quality characteristics of fermented tofu. The results showed that the yield of tofu was significantly increased by the fermentation of L. casei (24.75-31.26%). There was no significant difference in the WHC of the tofu, and the value range of WHC was 77.32-80.52%. Fermentation increased the hardness of the tofu and made the tofu structure uniform. In L. casei + MgSO₄ tofu, 10 flavour compounds were detected, and the relative content (54.29%) of the four main flavour compounds was highest. L. casei + MgSO₄ had the highest sensory value (23.26). The fermentation of L. casei combined with salt coagulants significantly improved the quality characteristics of tofu.

Influence of malondialdehyde-induced modifications on physicochemical and digestibility characteristics of whey protein isolate

Impacts of lipid oxidation product malondialdehyde (MDA) on the properties of whey protein isolate (WPI) were investigated in this study. The incorporation of MDA into WPI promoted the formation of protein carbonyls, with the significant loss of protein sulfhydryls, impaired intrinsic fluorescence, and increased protein surface hydrophobicity. The visualized band profiles revealed by gel electrophoresis and immunoblotting suggested that WPI's main components β-lactoglobulin and α-lactalbumin were the targets of MDA, and the derivatives of MDA were involved in protein cross-linking and aggregation at higher molecular weights. Abnormal protein aggregation was further confirmed by scanning electron microscopy analysis of the surface microstructure of MDA-modified WPI. Finally, in vitro digestibility assay indicated that the modification of MDA reduced WPI's susceptibility to digestive enzymes. The present study demonstrated that the contribution of MDA to protein modification in dairy products can be substantial in complex foodstuffs composed of lipids and proteins. PRACTICAL APPLICATIONS: The present work enhanced our knowledge on the remarkable susceptibility of dairy product WPI to lipid oxidation product MDA. With the trend of application of highly unsaturated fatty acids such as fish oil or alga oils as functional ingredients in dairy products, it is obvious that apart from monitoring lipid oxidation products, the resultant changes in dietary proteins deserve more attention. The food industry must be aware of the importance of appropriate preventive measures in minimizing the negative effects of lipid oxidation products on dairy products.

Processing milk causes the formation of protein oxidation products which impair spatial learning and memory in rats

This study explored the effects of protein oxidation during milk processing on spatial learning and memory in rats. Increasing the heating time, fat content, and inlet air temperature during processing by boiling, microwave heating, spray-drying, or freeze-drying increases milk protein oxidation. Oxidative damage done to milk proteins by microwave heating is greater than that caused by boiling. Dityrosine (DT), as a kind of tyrosine oxidation product, is the most important marker of this process, especially during spray-drying. Rats received diets containing either SWM (spray-dried milk powder diet), FWM (freeze-dried milk powder diet), FWM + LDT (freeze-dried milk powder + low dityrosine diet, DT: 1.4 mg kg-1), or FWM + HDT (freeze-dried milk powder + high dityrosine diet, DT: 2.8 mg kg-1) for 6 weeks. We found that the SWM group, the FWM + LDT group, and the FWM + HDT group appeared to have various degrees of redox state imbalance and oxidative damage in plasma, liver, and brain tissues. Further, hippocampal inflammatory and apoptosis genes were significantly up-regulated in such groups, while learning and memory genes were significantly down-regulated. Eventually, varying degrees of spatial learning and memory impairment were demonstrated in those groups in the Morris water maze. This means that humans should control milk protein oxidation and improve the processing methods applied to food.

Effects of Lung Protective Ventilation on the Cognitive Function Level of Patients with Esophageal Cancer

BACKGROUND

We intended to investigate the effects of lung protective ventilation on the cognitive function level of patients with esophageal cancer.

METHODS

Overall, 132 patients with esophageal cancer admitted to Taian Central Hospital, Taian China from January 2013 to January 2017 were enrolled in the study. According to the random number table method, they were divided into observation group and control group, 66 cases each. All patients underwent general anesthesia for thoracoscopic esophageal cancer radical operation, and lung protective ventilation and conventional positive pressure ventilation were used respectively. The levels of SOD, NSE and MDA, MMSE score and WMS memory quotient in the blood of the elbow vein were compared between the two groups at different times.

RESULTS

The levels of SOD and MMSE in the observation group at T2 and T3 were higher than those in the control group, and the NSE and MDA levels were lower than those in the control group (P=0.013, 0.033, 0.015, 0.044, 0.034, 0.029, 0.014, 0.017). The incidence of postoperative cognitive impairment was lower in the observation group than in the control group (P=0.007). The WMS memory quotient scores of the patients in the T2, T3, and T4 observation groups were higher than those in the control group (p=0.009, 0.032, 0.040).

CONCLUSION

Lung protective ventilation can reduce the oxidative stress injury for patients and improve their postoperative cognitive function and memory ability.

Effect of malondialdehyde on the ovalbumin structure and its interactions with T84 epithelial cells

BACKGROUND

Protein oxidation can occur as a consequence of lipid peroxidation during food processing. The aim of this work was to explore the effect of malondialdehyde (MDA) modification of ovalbumin (OVA) on its interaction with T84 intestinal cells.

METHODS

Molecular dynamics simulation was employed for the prediction of MDA modification in the OVA, while introduced structural changes were evaluated by measurement of carbonyl group content, fluorescence spectra, MS/MS analysis, and IgE reactivity. Effects of MDA modified OVA on T84 epithelial cells were analyzed by gene expression for pro-inflammatory cytokines and protein secretion.

RESULTS

Out of 9 predicted, five modified Lys residues were confirmed by MS/MS analysis: ⁵¹TQINKVVR⁵⁸, ⁸⁵DILNQITKPNDVYSFSLASR¹⁰⁴, ¹¹¹YPILPEYLQCVKELYR¹²⁶, ¹⁸⁷AFKDEDTQAMPFR¹⁹⁹, ²⁷⁷KIKVYLPR²⁸⁴, and ²⁷⁸IKVYLPR²⁸⁴. The introduced MDA modifications influenced profile of IgE reactivity to OVA. Treatment of T84 epithelial cells with OVA and OVA modified with 1mM MDA, induced up-regulation of pro-inflammatory cytokines (IL-1β, IL-25, IL-33, TSLP and TNFα), while OVA modification with 10mM MDA induced down regulation of the cytokine expression profile, except for IL-1β. OVA and OVA modified with 1mM MDA induced secretion of epithelial cells specific cytokine IL-33.

CONCLUSIONS

This finding indicated that OVA and its MDA modified form have the potential to trigger the innate immunity by inducing up-regulation and secretion of pro-allergenic IL-33 in T84 intestinal epithelial cells.

GENERAL SIGNIFICANCE

Interactions of ovalbumin and its MDA modified form with intestinal epithelial cells can induce a specific immunological priming necessary for the downstream activation of innate immunity.

Effect of magnesium salt concentration in water-in-oil emulsions on the physical properties and microstructure of tofu

The aim of this research was to prepare water-in-oil (W/O) emulsions encapsulating different concentrations of magnesium chloride (MgCl2) and to investigate the effect of W/O emulsions on the physical properties and microstructure of tofu. The results showed that the stability of W/O emulsions improved as the concentrations of polyglycerol polyricinoleate (PGPR) and MgCl2 increased. Dynamic viscoelastic measurements indicated that gelation time decreased with increasing MgCl2 concentration in W/O emulsions, suggesting a more rapid reaction between magnesium ions and protein molecules. As the concentration of MgCl2 in W/O emulsions increased, the yield and water content of tofu decreased, while the protein and crude fat contents and hardness values increased. At a concentration of 2.0M MgCl2 in W/O emulsion, the WHC and microstructure of the tofu samples were optimal. The variations in the physical properties of tofu were attributed to the concentration of magnesium ions and the coagulation rate.

Growth and physiological changes in continuously cropped eggplant (Solanum melongena L.) upon relay intercropping with garlic (Allium sativum L.)

Relay intercropping represents an alternative for sustainable production of vegetables, but the changes of internally antioxidant defense combined with the growth and yield are not clear. Field experiment was carried out to investigate the malondialdehyde (MDA) content and activity levels of superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) in eggplant (Solanum melongena L.) and plant height, stem diameter, maximal leaf area, and yield of eggplant grown under successive cropping in the year 2011 and 2012 to see if relay intercropping with garlic (Allium sativum L.) could benefit to eggplant growth and yield. Three experimental treatments with three repeats in each were carried out (completely randomized block design): eggplant monoculture (CK), eggplant relay intercropping with normal garlic (NG), and eggplant relay intercropping with green garlic (GG). In both years, the MDA content was significantly lower and SOD and POD activities were generally lower in NG and GG compared with CK in most sampling dates. PPO activity trends were generally opposite to those of POD. The general trend of PAL activity was similar to MDA. The plant height and stem of eggplant was lower, but the maximal leaf area was larger in NG and GG in 2011; in 2012 the plant growth was stronger in relay intercropping treatments. For eggplant yield in 2011, NG was 2.85% higher than CK; after the time for the green garlic pulled out was moved forward in 2012, the yield was increased by 6.26 and 7.80%, respectively, in NG and GG. The lower MDA content and enzyme activities in relay intercropping treatments showed that the eggplant suffered less damage from environment and continuous cropping obstacles, which promoted healthier plant. Thus from both the growth and physiological perspective, it was concluded that eggplant/garlic relay intercropping is a beneficial cultivation practice maintaining stronger plant growth and higher yield.

Effects of malondialdehyde modification on the in vitro digestibility of soy protein isolate

Soy protein isolate (SPI) was modified by lipid peroxidation product malondialdehyde (MDA), and the in vitro digestibility of modified SPI was investigated. Results indicated that incubation with increasing MDA concentration resulted in significant carbonyl group generation and loss of free amino groups of SPI. Fluorescence loss of natural tryptophan and formation of Schiff base were observed. Noncovalent interaction between molecules was enhanced and became the main force that led to the solubility reduction of MDA-modified SPI. Differential scanning calorimetry (DSC) indicated that SPI had higher thermal stability and lower total calorimetric enthalpy after MDA pretreatment. Electrophoresis showed that β-conglycinin was more sensitive to MDA modification. In vitro digestion indicated that MDA could induce non-disulfide covalent polymer of SPI, which could not be digested by pepsin and pancreatin. β subunits of β-conglycinin became more resistant to digestion with increasing MDA concentration. Evaluation of the free amino acid profile in the digests indicated that MDA-modified SPI had deteriorating nutritive quality.